They are only required to be no greater than 12.5 kHz wide in bandwidth. Just because they are still using a frequency that was assigned during the 25 kHz days doesn't mean they are still using that much bandwidth.
I don't know if you can tell just by listening to them on a scanner if they are compliant or not.
Right. The actual frequency is the same.
Yes; yes you can tell the difference by listening on the scanner. Well, at least you can if you're using older scanners
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When agencies first started converting over to "narrow band" you could tell right away because all their transmissions sounded like they were at half their usual volume. It was aggravating for me as a feed provider because I tried to find that perfect middle ground so you could hear the quiet and the loud didn't blow you away (and the loud ones would sound distorted).
Then when most of the agencies I monitored had converted, they were uniformly too quiet. I knew this because someone from RadioReference contacted and told me to turn up the volume (it was an admin of sorts).
So, everything is fine until TDOT starts broadcasting. It not all of their frequencies, just one or two. And it is bad, noticeably bad. It's not loud, it's just operating at the old, non-narrow band volumes. But, compared to the new low volume broadcasts, it's annoying. And their lack of radio etiquette makes it worse...